Pen to change Exposure sliders and Levels

Using a Wacom Intuos tablet with CaptureOne Pro 22.  Trying to use the pen to change the exposure sliders.  It will let me click on the lines and the slider jumps there, but can't seem to move the slider with the pen.  It did it one time and moved nice and smooth, but never again.  What is the trick?  Would be nice to have more docs on how to configure tablets for use with CO (apart from the one from 2014).